Nowadays, as template matching process, there is known a processing method in which a correlation value between the template image and the detection image is calculated in each position while a template image is shifted by one pixel each time_throughout an entire candidate area in a detection image, to thereby obtain a coordinate position at which the correlation value has the maximum value. The template matching process is performed in obtaining the position of an image in image processing and specifically, for example, in reproducing data by using a hologram reproducing technique. In the template matching process, the position or position-shift can be obtained by a pixel unit of the detection image.
On the other hand, there have been attempts to further improve the accuracy of the template matching process. For example, a patent document 1 discloses a technology in which a multivariate polynomial regression surface is used to obtain the position of the detection image by a sub-pixel unit. Moreover, a patent document 2 discloses a technology in which a difference or inclination (or slope) between the maximum value of the correlation values and the correlation value(s) around the position of the maximum value is used to obtain the position of the detection image by the sub-pixel unit. A patent document 3 discloses a technology in which the correlation value between pixels is complemented by a linear equation or curve equation on the basis of a positional relationship between the maximum value of the correlation values and the correlation value(s) around the position of the maximum value, to thereby obtain the position of the detection image by the sub-pixel unit.    Patent document 1: Japanese Patent Application Laid Open NO. Hei 5-120436    Patent document 2: Japanese Patent Application Laid Open NO. Hei 10-124666    Patent document 3: Japanese Patent Application Laid Open NO 2001-195597